Emptying starts soon after feeding; and movement of a meal through the stomach and small intestine into the large intestine is rapid, which results in only limited contact with the gastric secretions.
The rate of gastric emptying is dependent upon volume (and possibly energy density) - So the larger the meal, the more rapid the gastric emptying and the quicker the food passes through the small intestine; which in turn means there is less opportunity for digestion and absorption of nutrients.
A meal may well pass through the stomach in 20 minutes. And although it never completely empties, 95% of the DM intake will have gone by 12 hours - in most cases by 2 - 3 hours.